FAQ Can other plug-ins add actions to my part's context menu?

They can, but only if you want them to. If you want other plug-ins to be able to add actions to your part&#146;s context menu,
you need to do two things. First, you need to add a GroupMarker
instance to your context menu with the special ID IWorkbenchActionConstants.MB_ADDITIONS.
This placeholder tells the platform where actions
contributed by other plug-ins should appear in the context menu.

Second, when it is created, you need to register with the platform
your part&#146;s context menu by calling the IViewSite
or IEditorSite method registerContextMenu. If
it has more than one context menu, your part can contribute several
menus by defining a unique ID for each one. By convention, a part that has
only one context menu uses the part ID as the context menu ID.
You should publish these context menu IDs in your plug-in&#146;s
documentation so that other plug-in writers know what they are.